HIBA Azzeddine

SADI Salaheddine

Etude de la cinétique de recristallisation après déformation d’un alliage à base de magnésium

دشوشة نجاة

دراسة تأثير الشروط التجريبية على تطور الصلادة لسبيكة أساسها المغنيسيوم

بن الشيخ أميرة

Etude de synthèse sur la validité de la relation Hall-Petch dans les matériaux déformés et recristallisés

Chergui Loubna Achwaq

Evolution de la microstructure de l'alliage Mg-Ce après déformation par ECAP

Mejadi Amina

Evolution de quelques paramètres microstructuraux d'alliage déformé et recuit a base Mg

Hanna Abdelkader

Etude de quelques propriétés des alliages à base de magnésium après déformation pour utilisation comme biomatériaux

Yahiaoui Fatima Zohra

Cinétique de la recristallisation de l’alliage AZ31 après déformation par laminage

Hammou Fatima-Zohra

Contribution à l’étude de la corrosion dans un alliage à base de magnésium

KHAOUNI Farida

Modélisation de la texture de déformation par laminage d’un matériau polycristallin par le modèle VPSC (Visco-Plastic Self-Consistent)

Marzougui Malika

Contribution à l’étude de la texture cristallographique et de l'énergie stockée après hyper déformation de l'alliage Fe-36%Ni (% en poids)

Henni Ferdousse

Etude in situ par diffraction des rayons X synchrotron de la cinétique de la précipitation dans l’alliage hyper déformé Cu-Ni-Si

High-pressure torsion (HPT) processing is successfully applied to fabricate a novel hybrid material from separate discs of AZ31 (Mg–3Al–1Zn, wt%) and Mg–0.6Gd (wt%) alloys by straining through numbers of rotations, N, of 1/4, 1/2, 5, 10, and 20 turns at room temperature. The microstructure and texture are investigated near the bonding interface through the disc diameter using electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The microstructure exhibits two grain refinement regimes with the first occurring during an equivalent strain range, εeq, of ≈0.3–72 and the second during εeq from ≈72 to 517. The general texture changes from B-fiber to Y-fiber and C2-fiber through the HPT processing. The resultant microstructures and textures of this hybrid alloy are examined separately for the AZ31 and Mg-0.6Gd alloys and found controlled by the presence of twinning, slip systems, and second phases and the occurrence of different dynamic recrystallization mechanisms.

Citation

Hiba AZZEDDINE , ouarda ould mohamed, Y. Huang, T. Baudin, P. Bazarnik, F. Brisset, M. Kawasaki, T.G. Langdon, , (2023-01-01), Investigation of Microstructure and Texture Evolution in an AZ31/Mg–Gd Alloy Hybrid Metal Fabricated by High-Pressure Torsion, Adv. Eng. Mater., Vol:25, Issue:, pages:2201794, Wiley Online Library

The local microstructure, texture gradient and mechanical properties through the shoulder dimension (10 mm) of upper and lower AA5182 aluminum sheets were investigated using electron backscatter diffraction (EBSD) and Vickers microhardness after friction stir spot welding (FSSW). Based on the microstructural features (mean grain size, grain boundary type and dynamic recrystallization (DRX)), the upper sheet was found to be mainly composed of the stir zone (SZ) and thermomechanically affected zone (TMAZ) due to the high deformation induced simultaneously by the tool rotation and the shoulder download force, while the SZ, TMAZ, heat-affected zone (HAZ) and base metal (BM) were detected in the lower sheet due to the limited effect of the shoulder on the lower sheet. The texture changes, due to the nature of the deformation, demonstrated a shear-type texture at the SZ to a plane strain compression deformation type texture at the TMAZ and then a recrystallization texture at the HAZ and BM. The microhardness gradually decreased with the increasing distance from the keyhole along the SZ, TMAZ and HAZ regions. Eventually, the microstructure and microhardness evolutions were correlated based on the Hall–Petch relationship.

Citation

Hiba AZZEDDINE , T. Baudin, S. Bozzi, F. Brisset, , (2023-01-01), Local Microstructure and Texture Development during Friction Stir Spot of 5182 Aluminum Alloy, Crystals, Vol:13, Issue:3, pages:540, MDPI

The evolutions of microstructure and texture and the corrosion behaviour of low light rare-earth containing Mg-1.4Nd and low heavy rare-earth containing Mg-0.6Gd and Mg-0.4Dy (wt.%) were evaluated and compared after processing by high-pressure torsion (HPT) and isochronal annealing at 250 and 450 °C for 1 h using electron backscatter diffraction (EBSD) and electrochemical tests in a 3.5% (wt.%) NaCl solution. The EBSD results show that dynamic recrystallisation (DRX) was restricted in the Mg-1.4Nd alloy which led to a heterogenous deformation microstructure whereas the Mg-0.6Gd and Mg-0.4Dy alloys exhibited a homogenous deformation microstructure formed mostly of equiaxed dynamically recrystallised DRX grains. The HPT processing caused the development of a deviated basal texture in the three alloys. A good thermal stability of the three alloys was noticed after annealing at 250 °C. By contrast, annealing at 450 °C led to a homogenous equiaxed microstructure and weakening of texture for the Mg-1.4Nd alloy and a heterogenous bimodal microstructure with a stable basal texture for the Mg-0.6Gd and Mg-0.4Dy alloys. The HPT-processed Mg–RE alloys exhibited an improved corrosion resistance due to grain refinement. Thereafter, the corrosion resistance of the Mg-0.6Gd and Mg-0.4Dy alloys decreased with increasing annealing temperature due to an increase in grain size while the corrosion resistance of the Mg-1.4Nd alloy was improved after annealing at 450 °C due to precipitation and texture weakening.

Citation

Hiba AZZEDDINE , Achour Dakhouche , A. Hanna, T. Baudin, F. Brisset, Y. Huang, T.G. Langdon, , (2023-01-01), Evaluation of Thermal Stability and Its Effect on the Corrosion Behaviour of Mg-RE Alloys Processed by High-Pressure Torsion, Crystals, Vol:13, Issue:4, pages:662, MDPI

The microstructure and the corresponding crystallographic texture of the as-extruded WE54 alloy after natural aging for 11 years at room temperature have been characterized by the Electron backscatter diffraction (EBSD) technique. Before natural aging, the as-extruded WE54 exhibited equiaxed microstructure with a strong splitting basal texture and the presence of second particles along the extrusion direction (ED). Unexpectedly, long-term aging led to the formation of elongated deformed grains along ED having {11–20}<10-10> and {0001}<10-10> orientations with a partial development of fine static recrystallized grains by continuous and discontinuous mechanisms. It is believed that the origin of such grain structure development is the residual stored strain during the extrusion processing and the strain field induced from the solute Nd and Y atoms diffusion through the long-term natural aging. Artificial aging at 400 °C for 60 min demonstrated that the elongated deformed grains disappeared and left behind a heterogeneous recrystallized microstructure with a weak basal texture.

Citation

Hiba AZZEDDINE , T. Baudin, F. Brisset, , (2023-01-01), Effect of long-term natural aging on the microstructural characteristics of an extruded WE54 alloy, Current Applied Physic, Vol:54, Issue:, pages:38–43, Elsevier

In the present work, the grain growth activation energy, Q was evaluated in a Mg-0.3Ce (wt%) alloy after equal-channel angular pressing (ECAP) processing via route Bc for 4 passes at 300 and 350 °C and followed by isochronal annealing at 150, 250, 350, and 450 °C for 2 h. The results demonstrated that Q depends strongly on the deformation processing. The Q value was equal to 111.4 ± 5.7 kJ/mol for the sample ECAP-processed at 300 °C. While the sample ECAP-processed at 350 °C shows the presence of two different Q values depending on the annealing temperature, QI = 26.5 ± 3.4 kJ/mol in the low-temperature range (150–350 °C) and QII = 120.7 kJ/mol in the high-temperature range (350–450 °C). This behaviour was attributed to the resulting deformation microstructure and the occurrence of dynamic grain growth during ECAP processing at 350 °C.

Citation

Hiba AZZEDDINE , SALAHEDDINE SADI , A. Hanna, T. Baudin, F. Brisset, J. M. Cabrera, , (2023-01-01), Grain growth activation energy of ECAP-processed Mg-Ce alloy: Effect of deformation temperature, Materials Today Communications, Vol:37, Issue:, pages:107161, Elsevier

The static recrystallization/grain growth kinetics of the AZ31 (Mg-3Al-1Zn, wt%) alloy were investigated employing Vickers microhardness and electron backscatter diffraction (EBSD) measurements. The AZ31 alloy was subject to a hot-rolling for 70% of thickness reduction and then annealed at various temperatures (150 C, 250 C, and 350 C) from 5 min to 24 h. First, the static recrystallization kinetics were analysed by means of the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. The results showed that the recrystallization occurred under two regimes both involving their own Avrami exponent/activation energy. In regime I, the Avrami exponent was found in the range of 1.5-0.35 depending on the annealing temperature and activation energy of 74.1±5.7 kJ× mol-1. In regime II, an identical value of Avrami exponent was found (0.1-0.2) and a very low activation energy of 14.8±0.7 kJ× mol-1 was found for all annealing conditions. Non-random nucleation sites such as shear bands were considered as the main factor responsible for the deviation from the JMAK model. Moreover, the grain growth kinetics was well fitted by the general equation where. Accordingly, Q g= 109±0.2 kJ× mol-1 which is median between grain boundary diffusion and bulk diffusion values for Mg and its alloys. The derived activation energies were discussed in terms of influencing factors such as solute drag, formation of basal texture, and microstructural heterogeneities like shear bands and twinning.

Citation

SALAHEDDINE SADI , Hiba AZZEDDINE , Abdelkader Hanna, Thierr Baudin, Anne-Laure Helbert, François Brisset, Djamel Bradai, , (2022-12-12), Evaluation of static recrystallization and grain growth kinetics of hot-rolled AZ31 alloy, Journal of Metals, Materials and Minerals, Vol:32, Issue:1, pages:12-26, scopus

AA6060 aluminum alloy was subjected to severe plastic deformation through equal-channel angular pressing (ECAP) up to 8 passes via route BC. ECAPed samples isochronally annealed for 1 hour at a temperature range of 150-450 °C. The microstructure and texture of the studied material were evaluated by electron backscatter diffraction, and the microhardness was characterized by Vickers microhardness testing. It was found that shearing texture is typically enhanced after ECAP processing. Grain size and grain growth kinetics were also studied. ECAP led to a substantial rise in hardness, with stability following 4 passes. Microstructures and material properties were relatively stable up to annealing temperatures of 150 °C. Some sub-micrometer grains were kept in the 8 passes sample to annealing temperatures of 300 °C. Annealing at elevated temperature resulted in a reduction in hardness leading to a rise in grain size and a decrease in dislocation density. After annealing temperature up to 450 °C, the texture index reveals a tendency to the texture weakening and randomization. The activation energy required for the grain growth of the AA6060 alloy was exceptionally low above 300 °C.

Citation

Hiba AZZEDDINE , T. Khelfa, R. Lachhab, Z. Chen, J. A. Munoz, J. M. Cabrera-Marrero, F. Brisset, A.L. Helbert, T. Baudin, M. Khitouni, , (2022-12-12), Effect of ECAP and Subsequent Annealing on Microstructure, Texture, and Microhardness of an AA6060 Aluminum Alloy, Journal of Materials Engineering and Performance, Vol:31, Issue:, pages:2606–2623, Springer

Among the severe plastic deformation processing (SPD) of materials, high-pressure torsion (HPT) is known to induce considerable amounts of plastic strain and crucial grain refinement up to the nanometer scale. There have been several reviews on the mechanical properties and/or microstructure correlations of SPD-processed materials published during the last two decades. By contrast, a review on the crystallographic texture evolution during HPT processing is not at present available. Consequently, this work was undertaken to review the texture evolution in Face-Centered Cubic (FCC), Body-Centered Cubic (BCC) and Hexagonal Close-Packed (HCP) crystal structure materials processed exclusively by HPT with a special emphasis on the influence of many intrinsic and extrinsic factors such as the imposed strain, the deformation temperature and the alloying elements.

Citation

Hiba AZZEDDINE , D. Bradai, T. Baudin, T.G. Langdon, , (2022-01-01), Texture evolution in high-pressure torsion processing, Progress in Materials Science, Vol:125, Issue:, pages:100886, Elsevier

The residual strain determination by neutron diffraction has been performed on a set of five natural quartzite samples collected from Betic Cordilleras (Spain) and Sivas Basin (Turkey). The starting idea was to document an earlier conclusion about the texture components related either to deformation or recrystallization phenomena. Thereafter, as a consequence of the rock inhomogeneity, the complete strain tensor has been determined for each sample and discussed by taking into consideration the present-day knowledge in material sciences. The imposed macroscopic deformation observed at the sample locality led us to consider the form of the residual strain tensor as possibly representative of the natural finite plastic deformation suffered at the sample scale. Based on this, those tensors have been fitted to plastic tensors and introduced in texture simulations using a visco-plastic self-consistent (VPSC) model. The results demonstrate that the complete and meaningful strain tensor determination in rocks could be used as an experimental input in numerical modelling. This new combination of experimental and numerical approaches was validated and could help to better understand some geological phenomena.

Citation

Hiba AZZEDDINE , J.C. Guezou, M. Ceretti, T. Baudin, , (2022-01-01), Investigation of residual strain in quartzite using neutron diffraction: Interpretation and self-consistent modelling, Geological Journal, Vol:57, Issue:, pages:1125–1136, Wiley Online Library

The evolution of microstructure and texture during friction stir lap welding (FSLW) of TIMETAL 21S (β-type Ti-15Mo-3Nb-3Al-0.2Si, wt%) sheets were investigated through electron backscatter diffraction (EBSD). Excellent grain refinement is obtained through stir zone (SZ) thickness (1.2–1.8 μm). The microstructure of the thermomechanically affected zone (TMAZ) is characterized by elongated deformed grains surrounded by small recrystallized grains indicating the occurrence of discontinuous dynamic recrystallization (DDRX). The microstructure of heat affected zone (HAZ) is quite similar to the base metal (BM). The texture transformed from weak rolling-recrystallization texture in BM and HAZ to a typical shear texture with the domination of D1 or D2 components in the SZ and TMAZ area. A net shear texture gradient is formed across the SZ thickness which is connected with the heterogeneity of deformation. It is believed that the concomitant occurrence of grain size, dislocation and texture strengthening is responsible for the mechanical property distribution in different parts of FSLW joint.

Citation

Hiba AZZEDDINE , T. Baudin, F. Brisset, A. Zavdoveev, , (2022-01-01), Microstructure and texture characterization in friction stir lap welded TIMETAL 21S, Materials Characterization, Vol:19, Issue:, pages:112216, Elsevier

Static recrystallization and grain growth behaviors were investigated in Mg-0.3Ce (wt%) alloy processed by equal-channel angular pressing (ECAP) for N = 1 (εeq = 0.9), 2 (εeq = 1.9), and 4 (εeq = 3.9) passes at 300 °C using route Bc and annealed at 450 °C for 5, 30, 60, and 180 min. The results demonstrated that the annealed microstructure and texture are strongly related to the strain level, second particles distribution, and fraction of dynamic recrystallization (DRX) during ECAP. At low strain (1 ECAP pass), the microstructure was very heterogeneous and the texture development changed with increasing annealing time due to the absence of sufficient recrystallization nucleation sites and pinning effect of second particles. At medium strain (2 ECAP passes), the microstructure was homogeneous, however, the texture was unstable mainly due to the limited DRX during ECAP processing leading to the preferred grain growth. At high strain (4 ECAP passes), the microstructure was homogeneous and the texture was retained throughout the entire annealing duration due to the significant amount of DRX.

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SALAHEDDINE SADI , Hiba AZZEDDINE , Abdelkader Hanna, Thierry Baudin, Francois Brisset, Jose Maria Cabrera, , (2022), Microstructure and texture evolution of ECAP-processed Mg-Ce alloy during isothermal annealing, Materials Today Communications, Vol:32, Issue:, pages:103920, Elsevier

Static recrystallization of AZ31 alloy (Mg-3Al-1Zn, wt.%) is evaluated using Vickers microhardness and optical microscopy. The alloy was hot-rolled at 350°C for 70% of thickness reduction and then annealed at 450°C for periods ranging from 5 min to 24 h. The average grain size increases with increasing annealing time and reaches a value of 19 μm after 24 h. While the microhardness decreases from 64 Hv in the deformed condition to 56 Hv after annealing for 24 h.

Citation

SALAHEDDINE SADI , Hiba AZZEDDINE , Abdelkader Hanna, ,(2022), INVESTIGATION OF THE STATIC RECRYSTALLIZATION OF AZ31 MAGNESIUM ALLOY,Proceedings of 1st National Conference of Materials sciences And Engineering, (MSE’22),Khenchela

The microstructure and texture evolution of an AZ31 alloy were investigated after hot rolling and subsequent annealing using electron backscatter diffraction (EBSD). First, the alloy was hot-rolled at 350 ◦C up to low, medium and high strain (20, 50 and 85% of thickness reduction, respectively). The alloy samples where then annealed at 350 ◦C for 2, 10 and 60 min. The effect of strain level and annealing on corrosion behavior in seawater was also evaluated using electrochemical tests. At low strain, the microstructure was characterised by the absence of twinning, mainly due to the prior thermo-mechanical history of the as-received alloy. However, various modes of twinning were observed at medium strain. At high strain, the dynamic recrystallization process resulted in a microstructure with a typical basal texture. The results demonstrate that twins are responsible for the deviation of {0002} basal poles from normal towards the transversal direction. Annealing at 350 ◦C for up to 60 min led to normal grain growth in all the samples. In medium and highly strained samples, the deformation texture was retained, while the low strain sample underwent noticeable changes due to the absence of dynamic recrystallization. A synergetic effect of grain refinement and texture weakening was responsible for the alloy’s enhanced corrosion resistance.

Citation

Hiba AZZEDDINE , Achour Dakhouche , S. Tighiouaret, A. Hanna, L. Rabahi, F. Brisset, A-L. Helbert, T. Baudin, D. Bradai, , (2021-01-01), On the evolution of microstructure, texture and corrosion behavior of a hot-rolled and annealed AZ31 alloy, Materials Chemistry and Physics, Vol:267, Issue:, pages:124598, Elsevier

Experiments were conducted to evaluate the evolution of the stored energy in grains with shear texture orientations A*1{111} < 112 > , A*2{111} < 121 > , A {111} < 110 > , A{111} < 011 > , B {112} < 110 > , B{112} < 110 > and C {100} < 110 > for Cu-2.5Ni-0.6Si and Fe-36Ni (wt%) alloys after high-pressure torsion (HPT) processing up to 10 turns at ambient temperature using a Kernel Average Misorientation (KAM) approach. A typical stable shear texture developed in the Cu-2.5Ni-0.6Si alloy immediately after 1 turn whereas there was a continuous transformation of texture in the Fe-36Ni alloy up to 10 turns. The results show that HPT processing produces similar stored energies of ~35 J/mol and ~24 J/mol but with different shear texture components for the Cu-2.5Ni- 0.6Si and the Fe-36Ni alloy, respectively. The stored energy in all shear components for the Cu-2.5Ni-0.6Si alloy increases with increasing HPT processing up to 1 turn and then slightly decreases through 10 turns. By contrast, the stored energy of the Fe-36Ni alloy continuously decreases with increasing numbers of HPT turns. These evolutions are examined with reference to the initial textures, dynamic recrystallization, grain refinement mechanisms and differences in the stacking fault energies.

Citation

Hiba AZZEDDINE , T. Baudin, A-L. Helbert, F. Brisset, Y. Huang, M. Kawasaki, D. Bradai, T. G. Langdon, , (2021-01-01), A stored energy analysis of grains with shear texture orientations in Cu-Ni-Si and Fe-Ni alloys processed by high-pressure torsion, Journal of Alloys and Compounds, Vol:864, Issue:, pages:158142, Elsevier

The corrosion behaviour of as-cast binary Mg–0.3Ce, Mg–1.44Nd, Mg–0.63Gd and Mg–0.41Dy (wt%) alloys was investigated in DMEM + 10% FBS solution using electrochemical and weight loss tests. The results revealed that the alloys with heavy RE elements (Gd and Dy) exhibited the lowest corrosion rate compared to the alloys with light RE elements (Ce and Nd). The cytocompatibility of the Mg–RE alloys was assessed via live/dead straining after 3 and 7 days. The results show that Mg–0.63Gd alloy is a suitable candidate for biomedical applications.

Citation

Hiba AZZEDDINE , Achour Dakhouche , A. Hanna, B. Luthringer-Feyerabend, , (2021-01-01), Corrosion behavior and cytocompatibility of selected binary magnesium-rare earth alloys, Journal of Magnesium and Alloys, Vol:9, Issue:, pages:581-591, Elsevier

The characterization of microstructure and texture development of binary Mg-0.3Ce (wt%) after equal-channel angular pressing (ECAP) processing via route Bc at 300 and 350 °C through 4 passes were investigated using electron backscatter diffraction (EBSD) measurements. The results demonstrated an effective grain refinement from millimeter range to 6.7 and 8.3 μm obtained after 4 passes at 300 and 350 °C, respectively. The grain refinement was obtained through dynamic recrystallization (DRX). At 300 °C, DRX occurred at low strain by twin-induced dynamic recrystallization (TDRX) and particle stimulated nucleation (PSN) mechanism and then converted with increasing strain to sub-grain development (SD) and grain boundary bulging dynamic recrystallization (GBBDRX). Besides, grain growth occurred during processing at 350 °C. The texture development strongly depends on the strain level, deformation temperature and DRX mechanisms. At 300 °C, a typical basal texture with a deviation of 40° towards extrusion direction was formed gradually up to 4 passes while a completely different texture was formed at 350 °C due to the large grain size.

Citation

SALAHEDDINE SADI , Hiba AZZEDDINE , Abdelkader Hanna,, Casimir Casas, Thierry Baudin,, Anne-Laure Helbert,, François Brisset, Jose Maria Cabrera, , (2021), Characterization of microstructure and texture of binary Mg-Ce alloy processed by equal channel angular pressing, Materials Characterization, Vol:181, Issue:, pages:111454, Elsevier

In the present study, the through thickness morphological and textural characteristics of a Ni–14W sheet, processed by accumulative roll-bonding (ARB) up to 4 cycles (ε = 3.2) and annealed at 1100 °C for 1 h, were investigated using electron backscatter diffraction. In the internal layers, the microstructure exhibited a small grains size free of twins and contained high fraction of low angle grain boundaries due the domination of {001}〈100〉 Cube orientation. At the surface layers, grains were coarser and contained high fraction of twins, while texture was characterized by retained shear components. The results showed that the heterogeneity of annealed microstructure texture decreased with the increasing number of ARB processing. Particle stimulated nucleation mechanism was evidenced at the vicinity of some bonding interfaces due to the presence of metallic inclusions resulting from wire-brushing procedure. As a result, the orientation of the new recrystallized grains was rather random and the grain size was stabilized by a pining effect which contributed to the microstructure heterogeneity. A successful bonding was achieved with increasing number of ARB cycles as shown by the transformation of interfaces into grain boundaries and their subsequent migration.

Citation

Hiba AZZEDDINE , , (2020-12-10), Microstructural peculiarities and textural characteristics of Ni–W sheet alloy after accumulative roll-bonding and annealing, SN Applied Sciences, Vol:650, Issue:2, pages:1–13, Elsevier

The corrosion behaviour of Mg-0.3Ce, Mg-0.41Dy, Mg-0.63Gd, Mg-1.44Nd and Mg-1.43La (wt.%) alloys in 3.5 wt% NaCl solution was investigated using electrochemical tests. The as-cast microstructures of the Mg-RE alloys were characterized by the presence of second phases (MgxCe, Mg41Dy5, Mg12Gd, Mg12Nd, Mg41Nd5, Mg24Nd and Mg12La) with different volume fraction and distribution. Results show that the corrosion mechanism was altered from uniform to localized corrosion mechanism depending on the specific RE alloying elements. The corrosion resistance of the Mg-RE alloys is increasing in the following order: Mg-1.43La, Mg-1.44Nd, Mg-0.3Ce, Mg-0.63Gd and Mg-0.41Dy. Accordingly, the corrosion morphology in the best resistant Mg-0.41Dy alloy and the worst Mg-1.43La alloy were observed and compared after 2h and 24 h of immersion using SEM-EDS, XPS and XRD analysis. The formation of the Dy2O3 oxide prevents the Mg-0.41Dy alloy from pitting corrosion and lead to an excellent corrosion surface even after 24 h of immersion. Meanwhile, the presence of a high fraction of the Mg12La phase along the grains boundaries in the Mg-1.43La alloy causes severe pitting corrosion by acting as anodic phase.

Citation

Hiba AZZEDDINE , Achour Dakhouche , A. Hanna, L. Rabahi, N. Scharnagl, M. Dopita, F. Brisset, A.L. Helbert, T. Baudin, , (2020-01-11), Impact of rare-earth elements on the corrosion performance of binary magnesium alloys, Journal of Alloys and Compounds, Vol:829, Issue:, pages:154569, Elsevier

The present study investigates the deformation and recrystallization behaviour of a Mg-0.41Dy (wt.%) alloy processed via plane strain compression (PSC) at room temperature (RT), 200, and 400 °C under a strain rate of 10−4 s−1. PSC at RT and 200 °C causes the introduction of a high amount of deformation features, like extension, contraction, and double twins. Meanwhile, PSC at 400 °C is characterized by the occurrence of dynamic recrystallization. The change in the microstructures affects the mechanical response of the alloy. The deformation texture is characterized by the formation of basal<0001>and prismatic<10 1 0>fibres, while the texture intensity increases with increasing deformation temperature. The static recrystallization and grain growth kinetics were investigated for all processed samples after subsequent annealing at 450 °C for a time period ranging from 30 min to seven days. The evolution of grain size and microhardness strongly depends on the deformation temperatures. Moreover, the recrystallization rate increases with increasing deformation temperature. The Avrami exponent of recrystallization n was in the range of 0.26–0.9, indicating that the recrystallization preferentially occurs along grain boundaries and within deformation features.

Citation

Hiba AZZEDDINE , F. Guerza-Soualah,, A. Hanna, A.L. Helbert, F. Brisset, T. Baudin, D. Bradai, , (2020-01-01), The deformation and recrystallization behaviour of an Mg-Dy alloy processed by plane strain compression, Materials Today Communications, Vol:24, Issue:, pages:101239, Elsevier

rate of 10 −2 and 10 −4 s −1 up a final true strain of −1.2 were investigated using electron backscatter diffraction (EBSD) and X-ray diffraction. At high strain rate of 10 −2 s −1 , the microstructure exhibited massive twins mainly {10 ¯1 2} extension, {10 ¯1 1} contraction and { 10 ¯1 3}-{10 ¯1 2} double twin due to the random texture of the as-cast alloy. Meanwhile, at a low strain rate of 10 −4 s −1 , the microstructure was characterized by dynamic recrystallization at the {10 ¯1 2} extension, {10 ¯1 1} contraction twins and grain boundaries. Twin dynamic recrystallization (TDRX), rotational dynamic recrystallization (RDRX) and discontinuous dynamic recrystallization (DDRX) were the main mechanisms responsible for the formation of recrystallized grains. The texture was characterized by the formation of three fibers: basal < 0001 > , < 10 ¯1 0 > // CD and < 11 ¯2 0 > // CD where CD is the compression direction. Moreover, the texture was less sensitive to the deformation conditions since the recrystallized grains showed the same orientation than twins. The changes of the mechanical properties of the alloy were ascribed to the resulting microstructure due to the twinning and dynamic recrystallization.

Citation

Hiba AZZEDDINE , F. Guerza-Soualah,, T. Baudin, A.L. Helbert,, F. Brisset, D. Bradai, , (2020-01-01), Microstructural and textural investigation of an Mg–Dy alloy after hot plane strain compression, Journal of Magnesium and Alloys, Vol:8, Issue:, pages:1198-1207, Elsevier

The kinetics of Cr clustering process in a commercial Cu-1Cr-0.1 Zr (wt.%) alloy processed by equal channel angular pressing (ECAP) via route BC at room temperature for 1, 8 and 16 passes, has been investigated using Differential Scanning Calorimetry (DSC). The DSC scan results showed that the Cr clustering peak temperature reaction increases with increasing the heating rate and decreased with the imposed strain. The activation energy of clustering was estimated using Kissinger, Boswell and Ligero analytical methods. The obtained values were in the range of ∼137 and 144 kJ/mol. The Avrami parameter n was around unity which corresponds to a process of grain boundary nucleation after site saturation.

Citation

Hiba AZZEDDINE , Y.I. Bourezg, K. Abib, D. Bradai, , (2020), Kinetics of Cr clustering in a Cu-Cr-Zr alloy processed by equal-channel angular pressing: A DSC study, Thermochimica Acta, Vol:686, Issue:, pages:178550, elsevier

The local atomic structure of an Mg-1.44Nd (wt.%) alloy was investigated after solution annealing, high-pressure torsion (HPT) processing up to 1 and 10 turns and ageing at 250 °C for 5 h using X-ray absorption fine structure (XAFS) measurements at the Nd LIII-edge. The results show that HPT processing has no effect on the atomic structure around Nd atoms compared to the unprocessed state, whereas ageing at 250 °C for 5 h induces a significant modification in the coordination number and interatomic distances around the Nd atoms. These variations are analyzed based on the correlations between precipitation, defects and atomic mobility of the chemical species.

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Hiba AZZEDDINE , Y.I. Bourezg, M. Harfouche, D. Thiaudiere, C. Mocuta, Y. Huang, D. Bradai, T.G. Langdon, , (2020), An investigation by EXAFS of local atomic structure in an Mg-Nd alloy after processing by high-pressure torsion and ageing, Materials Letters, Vol:264, Issue:, pages:127379, elsevier

The stored energy and activation energy for recrystallization were investigated for a Cu-Ni-Si alloy after high-pressure torsion processing for N = ½, 1, 5 and 10 turns at room temperature. The contributions of geometrically necessary dislocations (GNDs), statistically stored dislocations (SSDs) and vacancies to the stored energy were calculated through the Vickers microhardness measurements, kernel average misorientation (KAM) measurements and an analysis by differential scanning calorimetry (DSC). The results show that the total stored energy decreases rapidly after equivalent strain of εeq ∼ 9 and then saturates through εeq ∼ 86 at ∼70 J/mol. Concurrently, the local stored energy in GNDs and SSDs was found to depend strongly on the radial distance from the centre of the disc and increase with increasing equivalent strain at εeq ∼ 16 and saturate with further straining. Accordingly, the results indicate that the GNDs and vacancies are responsible for the high stored energy in the initial stage of deformation at equivalent strain range of εeq = 8.6–16 and thereafter their contribution decreases slightly due to the occurrence of dynamic recrystallization and the formation of fine grains. At the same time, the contribution of the SSDs is similar to that of the GNDs only in high strain deformation as at εeq = 49.3 to accommodate the deformation process. An activation energy for recrystallization was estimated in the range of ∼ 89.7–98.7 kJ/mol, thereby suggesting poor thermal stability.

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Hiba AZZEDDINE , Y.I. Bourezg, A.Y. Khereddine, T. Baudin, A.L. Helbert, F. Brisset, M. Kawasaki, D. Bradai, T.G. Langdon, , (2020), An investigation of the stored energy and thermal stability in a Cu–Ni–Si alloy processed by high-pressure torsion, Philosophical Magazine 100 (2020) 688-712, Vol:100, Issue:6, pages:688-712, Taylor & Francis

Samples of an Mg-0.41Dy (wt. %) alloy were severely deformed by high-pressure torsion (HPT) at room temperature up to 15 turns and the texture, microstructure and microhardness values in the centres, mid-radial points and edges of the HPT-deformed discs were investigated using X-ray diffraction, Electron BackScatter Diffraction and Vickers microhardness measurements. The textures in the centres of discs were characterized by a typical weak basal fiber whereas at both the mid-points and edges of the discs there was a strong basal texture where the c-axis of most grains was shifted 15° away from the shear direction. An almost homogeneous ultrafine-grained structure with a grain size of about 0.75 μm was achieved after 15 HPT turns. The microhardness values in these three positions increased with increasing numbers of turns, reached a maximum and then decreased to a lower steady-state level at large strains. In addition to dislocation and grain size hardening, the results show that texture strengthening contributes significantly to the rapid increase in hardening in the early stages of deformation.

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abdelkader hanna , Hiba AZZEDDINE , Rabeb Lachhab, Thierry Baudin, Anne Laure Helbert, François Brisset, Yi Huang, Djamel Bradai, Terence G. Langdon., , (2019), Evaluating the textural and mechanical properties of an Mg-Dy alloy processed by high-pressure torsion, Journal of Alloys and Compounds, Vol:778, Issue:, pages:61–71, elsevier

The evolution of microstructure, texture, and mechanical properties of an Mg–1.43Nd (wt%) alloy is investigated after processing by high‐pressure torsion at room temperature through five turns and isochronal annealing for 1 h at 150, 250, 350, and 450 °C using electron backscatter diffraction and Vickers microhardness. The alloy exhibits a good thermal stability up to annealing at 250 °C, with mean grain size of ≈0.65 μm. The microhardness shows an initial hardening after annealing at 150 °C and then a subsequent softening. The deformation texture, a basal texture shifted 60° away from the shear direction (SD), is retained during annealing up to 250 °C. In contrast, a basal texture with symmetrical splitting toward SD is developed after annealing at 350 °C. The precipitation sequence and their pinning effects are responsible for the age‐hardening, stabilization of grain size, and the texture modification. The kinetics of grain growth in the Mg–1.43Nd alloy follows two stages depending on the temperature annealing range, with an activation energy of ≈26 kJ mol−1 in the low temperature range of 150–250 °C and ≈147 kJ mol−1 in the high temperature range of 250–450 °C.

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Tighiouaret Samia , abdelkader hanna , Hiba AZZEDDINE , Rabeb Lachhab, Y. Huang, T. Baudin, A-L. Helbert, F. Brisset, D. Bradai, T.G. Langdon, , (2019), Thermal Stability of an Mg–Nd Alloy Processed by High-Pressure Torsion, Advanced Engineering Materials, Vol:21, Issue:12, pages:1900801, Wiley Online Library

An Mg-0.41Dy (wt%) alloy was successfully processed by high-pressure tension (HPT) through 5 turns at room temperature. The evolution of the recrystallization microstructure and the texture and mechanical properties of the deformed alloy were investigated after annealing at 200 and 400 °C for 1 h using Electron Backscatter Diffraction (EBSD) and Vickers measurements. The recrystallization temperature and activation energy were evaluated using Differential Scanning Calorimetry (DSC). Processing by HPT led to significant grain refinement with an average grain size of ~0.5 ± 0.1 μm which increased to ~1.2 ± 0.8 μm after annealing at 400 °C. This slow increase in grain size at a high temperature demonstrates a good thermal stability of the microstructure. The alloy exhibited two main fiber textures after HPT processing: firstly a typical basal fiber (φ1 = 0–360°, Φ = 0° and φ2 = 0–60°) and secondly a fiber localized at φ1 = 180°, Φ = 60° and φ2 = 0–90°. These textures were retained after annealing at 400 °C. There was no change in the microhardness value after annealing at 200 °C (41 ± 1 Hv) and only a minor decrease after annealing at 400 °C (38.4 ± 0.5 Hv). The DSC results showed that the temperature associated with the recrystallization process increased with increasing heating rate and the activation energy for recrystallization was measured as ~25 kJ mol−1.

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abdelkader hanna , Hiba AZZEDDINE , Y. Huang, D. Bradai, J. M. Cabrera, T. G. Langdon, , (2019), An investigation of the thermal stability of an Mg-Dy alloy after processing by high-pressure torsion, Materials Characterization, Vol:151, Issue:, pages:519–529, elsevier

The precipitation of nano-sized Cr clusters was investigated in a commercial Cu-1Cr-0.1Zr (wt.%) alloy processed by equal-channel angular pressing and subsequent aging at 550 °C for 4 h using Small-Angle Neutron Scattering (SANS) measurements and High-Angle Annular Dark-Field-Scanning Transmission Electron Microscopy (HAADF-STEM). The size and volume fraction of the nano-sized Cr clusters were estimated using both techniques. The parameter values assessed by SANS (d ∼ 3.2 nm, Fv ~ 1.1 %) agreed reasonably with those by HAADF-STEM (d ∼ 2.5 nm, Fv ∼ 2.3 %). In addition to the nano-sized Cr clusters, HAADF-STEM indicated the presence of rare cuboid and spheroid sub-micronic Cr particles measuring approximately 380–620 nm in mean size. Both techniques did not evidence the presence of intermetallic CuxZrz phases within the aging conditions.

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Hiba AZZEDDINE , K. Abib, B. Alili, L. Litynska-Dobrzynska, A. L. Helbert, T. Baudin, P. Jegou, M. H. Mathon, P. Zieba, D. Bradai, , (2019), Cr cluster characterization in Cu-Cr-Zr alloy after ECAP processing and aging using SANS and HAADF-STEM, Kovove Materialy-Metallic Materials, Vol:57, Issue:2, pages:121–129, Slovak Academy of Sciences

The effect of initial texture on the microstructure and texture evolution of as extruded AZ31 alloy after hot uniaxial compression at 430 °C and subsequent annealing at 450 °C for 72h has been investigated using electron backscatter diffraction. Samples were machined from the extruded block in such orientations that the compression axis, CD, was parallel (CD0ED) or perpendicular (CD90ED) to the initial extrusion direction, ED, respectively. Results show that the deformation microstructure for both samples was characterized by equiaxed grains that resulted from dynamic recrystallization. Annealing at 450 °C for 72 h led to the increase of grains size to 28 and 25 µm for CD0ED and CD90ED samples, respectively. A random deformation texture was developed in CD0ED sample while the deformation of CD90ED developed typical (0002) basal texture. The deformation textures of both samples were retained after subsequent annealing at 450 °C for 72 h. The flow behavior was affected by the initial texture. The CD0ED sample showed the highest work hardening. These evolutions were explained in term of the activation and suppression of basal, non-basal slip and mechanical twinning.

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abdelkader hanna , Hiba AZZEDDINE , Fadi Abouhilou, Djamel Bradai, , (2019), Microstructure and texture evolution of AZ31 Mg alloy after uniaxial compression and annealing, Journal of Magnesium and Alloys, Vol:7, Issue:1, pages:124–133, National Engineering Research Center for Magnesium Alloys of China, Chongqing University

A Fe–48wt%Ni alloy was processed by severe plastic deformation using equal channel angular pressing process. A stacking of 9 sheets was introduced and pressed up to two passes into die with an inner angle of Φ = 90º and outer arc of curvature ψ = 17° at room temperature following route A. The same material in bulk form was also ECAPed up to one pass. The microstructure and the texture were investigated by means of electron backscattered diffraction and X-ray diffraction, respectively. To evaluate the mechanical response, Vickers microhardness was carried out. The given analyses concern the as-received sample, the peripheral and the central plates of the pressed stacks and the upper, the middle and the lower parts of the pressed bulk material. The deformation was heterogeneous, and variations in texture and microstructure, resulting from different efficiencies in the shearing process, were locally noted. For the stacks samples, the microstructure evolved from equiaxed grains of 9 μm with high fraction of high-angle grain boundaries (around 90%) to a heterogeneous fine grain structure with an average grain size of 3 μm after two passes. On the contrary, for the bulk sample, the evolution was to a banded structure after one pass. Results of mechanical property show that microhardness increased significantly from 147 Hv before deformation to mean values of 244 (after one pass) and 235 Hv (after two passes) for the bulk and stacked samples, respectively. The Hall–Petch effect and dislocation density were evaluated as most responsible in material strengthening.

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Hiba AZZEDDINE , R. Lachhab, M. A. Rekik, T. Baudin, A. L. Helbert, F. Brisset, M. Khitouni, , (2019), Study of the microstructure and texture heterogeneities of Fe-48wt%Ni alloy severely deformed by equal channel angular pressing, Journal of Materials Science, Vol:54, Issue:, pages:4354–4365, Springer

The microstructure and texture of an Al1050/AZ31/Al1050 laminated composite fabricated by accumulative roll bonding at 400 °C up to 5 cycles are investigated using Electron BackScatter Diffraction, neutron diffraction, microhardness measurements and tensile tests. EBSD analysis has shown that ARB processing led to microstructural refinement with equiaxed grain microstructure in AZ31 layers and to the development of elongated grains parallel to the rolling direction in Al 1050 layers. No new phases formed at the bond interface after the first ARB cycle while Mg17Al12 and Mg2Al3 phases appeared after subsequent cycles. During the ARB processing, a typical strong basal (0002) texture is observed in AZ31 layers along with a weak rolling texture showed in Al 1050 layers with a dominant Rotated Cube {001}〈110〉 component. The microhardness of Al1050/AZ31/Al1050 laminated composite increased with increasing ARB cycles and almost saturated after five ARB cycles. The yield strength and ultimate strength increased gradually between 1 and 3 ARB cycles due to the strain hardening and grain refinement. They decreased with further increasing of the ARB cycles because of crack and failure of the MgxAly intermetallic compounds which developed during 4th and 5th ARB cycles. The deformation behavior of the laminated composite becomes rather similar to the behavior of AZ31 alloy that underwent a dynamic recrystallization during processing.

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Hiba AZZEDDINE , W. Habila, B. Mehdi, K. Tirsatine, T. Baudin, A. L. Helbert, F. Brisset, S. Gautrot, M. H. Mathon, D. Bradai, , (2019), Investigation of microstructure and texture evolution of a Mg/Al laminated composite elaborated by accumulative roll bonding, Materials Characterization, Vol:147, Issue:, pages:242-252., Elsevier BV

The aim of the present study is to investigate the effect of deformation conditions on the corrosion behavior of AZ31 (Mg-3Al-1Zn, % wt.) in 0.9% NaCl (wt.%) solution. The AZ31 alloy was hot rolled at 360 °C to 20 and 50% of thickness reduction. Electrochemical measurements were used to study the corrosion behavior of AZ31 alloy. Analysis of corrosion products after immersion test was performed using optical microscopy, X-ray diffraction and Raman spectroscopy. The mechanical properties of corroded samples were investigated using tensile test at room temperature. Results indicated that the corrosion rate was strongly affected by the hot rolling level. A lower corrosion potential and reduced polarization resistance was observed after hot rolling compared to the as received AZ31 alloy. The corrosion product was evidenced mainly as Mg(OH)2 compound exhibiting a filiform-like morphology. Apparently, the corrosion improved the room temperature ductility of AZ31 alloy.

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abdelkader hanna , Achour Dakhouche , Hiba AZZEDDINE , K. Tirsatine, A. Sari, Y. Khereddine, D. Bradai, , (2019), Effect of hot rolling on the corrosion behavior of AZ31 magnesium alloy, Metallurgical Research & Technology, Vol:116, Issue:, pages:109, EDP Sciences

The microstructure, texture and mechanical properties of the Ni-14%W (wt.%) alloy with two different initial grain sizes and textures were investigated after groove pressing (GP) at 450 °C to 4 cycles using electron back scatter diffraction (EBSD) and microhardness measurements. The first series (I) was characterized by small equiaxed grains and cube dominant texture component, whereas the second series (II) had elongated grains and β-fiber texture. EBSD analysis has shown that GP processing led to a slight refinement (less than 15 %) of equiaxed grains in series I while greater refinement (∼ 55 %) of the mean spacing along normal direction was observed in series II. The texture did not drastically change from the initial one and was characterized by the weakening of the cube component in series I and rapid decrease of the copper component for series II. GP processing reduces the plastic anisotropy of the alloy with initial elongated granular microstructure very slightly

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Hiba AZZEDDINE , S. Koriche, S. Boudekhani-Abbas, K. Abib, A.L. Helbert, F. Brisset, T. Baudin, D. Bradai, , (2018), On the groove pressing of Ni-W Alloy: microstructure, texture and mechanical properties evolution, Kovove Materialy-Metallic Materials, Vol:56, Issue:, pages:313–323, Slovenska Akademia Vied

In this study, the microstructure, texture, and mechanical properties evolution of Ni-14W (wt.%) alloy processed up to four cycles of accumulative roll-bonding (ARB) were investigated using electron backscatter diffraction, microhardness measurements, and tensile tests. The initial equiaxed grains, with an average size of 10 μm, underwent a strong refinement after ARB processing. The elongated ultrafine grains were parallel to the rolling direction, with a grain thickness of 0.2 µm. The texture after ARB processing was characterized by the typical rolling components (Copper, S and Brass), which showed a tendency toward stabilization after four cycles. The microhardness increased substantially (+ 86%) and seemed to saturate after three cycles. The tensile tests demonstrated that Ni-14W samples subjected to ARB processing exhibited high strength (> 1200 MPa after three ARB cycles) and very poor ductility.

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Hiba AZZEDDINE , S. Boudekhani-Abbas, K. Tirsatine, T. Baudin, A-L. Helbert, F. Brisset, B. Alili, D. Bradai, , (2018), Microstructure, Texture and Mechanical Properties of Ni-W alloy after Accumulative Roll Bonding, Journal of Materials Engineering and Performance, Vol:27, Issue:, pages:5561-5570., Springer

The evolution of stored energy associated with Brass {110}<112>, Copper {112}<111>, S {231}<346> and Cube {001}<100> texture components of Fe-36Ni (wt.%) Invar alloy after accumulative roll-bonding (ARB) processing up to 6 cycles was investigated using two methods: Neutron Diffraction peak broadening analysis and Kernel Average Misorientation (KAM) in an electron backscatter diffraction (EBSD). Both methods evidence the stored energy evolution variation as ECopper > ES > EBrass > ECube. The stored energy increases first with strain up to 3 cycles and then decreases and then slightly rises up again between 4 and 6 cycles but with a trend towards stabilization. The overall evolution of the stored energy versus strain was related to the dislocation density and substructure evolution as well as recovery process. The small increase of the stored energy at high deformation levels is due to the production of new dislocations. Comparisons between results obtained with the two methods and with Dillamore approach show that Geometrically Necessary Dislocations (GND) dislocations in the cells/sub-grains walls are the principal contributor to the stored energy of the alloy.

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Hiba AZZEDDINE , K. Tirsatine, T. Baudin, M.H. Mathon, A.L. Helbert, F. Brisset, D. Bradai, , (2017), On the stored energy evolution after accumulative roll-bonding of invar alloy, Materials Chemistry and Physics, Vol:201, Issue:, pages:408-415, elsevier

The texture evolution of Fe-36%Ni(wt%) alloy processed by accumulative roll-bonding (ARB) up to six cycles was investigated using neutron diffraction. The texture sharpened after the second cycle, showed continuous strength up to six cycles, and was characterized by the typical copper-type texture together with a R-Cube{001}<110> component that appeared after two cycles of ARB processing. The texture obtained by neutron diffraction was compared with that measured by electron backscatter diffraction (EBSD). The neutron diffraction and EBSD texture intensities were substantially similarand exhibited almost the same trends for all texture components. The evolution of the Lankford coefficient R, average Lankford factor , planar anisotropy ΔR, and Young modulus values versus angle to rolling direction calculated from experimental textures of ARBed samples showed that ARB processing increased the plastic anisotropy and Young modulus of the sheet.

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Hiba AZZEDDINE , K. Tirsatine, T. Baudin, A.L. Helbert, M.H. Mathon, F. Brisset, D. Bradai, , (2017), Neutron diffraction versus EBSD analysis of the texture in Fe-36%Ni alloy after accumulative roll bonding, Indian Journal of Engineering & Materials Sciences, Vol:24, Issue:, pages:35-44, Scientific Publishers

Le but principal de cet ouvrage est d’aider à la compréhension des évolutions de la texture des matériaux métalliques. Par texture cristallographique, on entend les orientations préférentielles des grains qui constituent le poly-cristal. Cette texture joue un rôle déterminant pour l’évolution des propriétés mécaniques lors et après déformation plastique pour la mise en forme des matériaux. Depuis trois décades, de nombreuses techniques de déformation plastique ont été inventées. Elles ont pour but d’affiner la microstructure en dessous du micromètre (jusqu’à quelques dizaines de nanomètres, parfois). Ces techniques innovantes sont dites « Techniques de déformation plastique sévère » ou hyper déformations. Avec les microstructures et textures obtenues après hyper déformation, les matériaux acquièrent des propriétés physiques, métallurgiques et mécaniques remarquables. Cet ouvrage présente les principales connaissances sur la texture, les techniques expérimentales pour sa mesure ainsi que des résultats de calcul de la texture pour différents matériaux (ayant des symétries cristallines différentes) après déformation plastique conventionnelle et sévère. Cette monographie intéresse les étudiants du deuxième et troisième cycle LMD aussi bien que les chercheurs confirmés, ingénieurs en Recherche et développement (RD) en matériaux.

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HibaAZZEDDINE , Djamel Bradai, ,(2016); Texture cristallographique dans les matériaux,,OPU